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Discussion Starter · #1 · (Edited)
Question on this.. If someone were to put a 6BT in a rig that is ~ half ton, it fits and works well doing it and is clean but some of the axle components might show early fatigue if left at a stock power range.. Also in the effort of FUEL MILEAGE, is this possible with this era 6BT motor, to detune it? Can you detune significantly for better mileage and actually having less overall power?

The idea is for something like this, a FJ60 land Cruiser.. With adequate springs in the front these have been fine for 6BTs and several have had them installed. This is wishful thinking for my GF/future wife, who loves diesels and loves this era of Land Cruiser and I think it would be a neat combo/camping/DDer/light towing rig.. Any comments? I would love to see it get 25 mpg. But also be able to tow a little better than a 4BT when needed. Something like 200 hp or so...
 

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It is possible however your 200 hp baseline starting point is a bit high if you intend on going with an 89-93 first generation engine. They are factory rated at 160 hp/400 tq. It's the 400 tq side that would be the most destructive part to deal with. I would imagine that by backing out the fuel screw you could back that down a bit but you could run into a lean mixture & increased exhaust gas temperature if you went too far. (Blacksmith bellows effect) I think you could back her down to the 120-130 hp range and end up in the neighborhood of 30 mpg or more.

When I bought my 91 Dodge Cummins we had a long conversation. PO said he owned the truck for around five years. It ran like a slug for the first four years but it consistently got 25+ mpg. He then had the pump tweaked and it ran like a completely different truck. The down side was that after tweaking the pump the mileage has dropped to a consistent 20 mpg. This is in a 4WD 6300 pound truck. The increased power also took its toll on the marginal 5 speed transmission which lost its input bearing. So I bought it with a tore up transmission which I converted into a NV4500 and probably while it is not the cheapest truck but probably the best truck I ever bought in my 40+ years of driving. bounce
 

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Up untill 1998.5 the 6bt in dodges only had 215hp. The first gen with VE pump had 160hp, 94-96 had 180hp i think so would you really need to detune?. The 4bt would definitely be better for mileage alone. You would have to drive like a granny on a budget to get 25mpg with a 6bt. The 6bt are more plentiful and less expensive.The easiest way to detune would be with your right foot. But if you are after 200bhp isnt 215hp near enough?. If your vehicle can handle a 6BT both size & weight and mileage isn't your only concern I would go 6bt everytime. JMHO

Gaza
 

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Discussion Starter · #4 ·
I am aware of detuning with the gen 1 dodges, the VE pump, just like the 4BTs.. I have been hearing of 22 mpg with the Dodges at stock settings, so I don't think 25 would be too out of line. Ideally I would like to use that later inline pump 6BT from a '94-'98.5. Reason I am intersted in this one is because its more efficient, more power for similar fuel consumption versus the gen 1 Dodges. So I figured detuned it would be even more efficient? Honestly everything will hold up fine drivetrain-wise I figure. there may be some issued but they are actually built strong. For the reasons 66gaza mentioned, though of course I love the 4BTs and have one in my FJ55, I was thinking a 6 cyl for this one. And again for towing as necessary, some cars here and there, a smaller camper trailer, loading down with gear etc... This is all a pipe dream/wishful thinking but figured I would post/ask.. :beer:
 

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That's a nice looking truck!

I see where you're coming from but I don't know if a 6BT is the best way to get where you want. As mentioned, one thing you can't really de-tune is the torque monster in a 6BT. The problem isn't even the torque alone, but more the rpm it occurs at: off idle. A non-diesel may put out similar torque, say 400 ft lbs, but it happens much farther up the rpm band. At lower speeds it's probably only 150-175 ft lbs.

With a diesel the entire drivetrain is hit with the 400 ft lbs off idle, as from a standing start, every single time you let it loose. The strain comes from getting the vehicle mass rolling from a stand still. 400 ft lbs is hitting the torque converter and clutches, or the clutch and drivetrain etc.

I plan to tow a lot with my 4BT in a 5,200 lbs vehicle. I don't plan to tweak much, maybe 140-150 hp, and 500 ft lbs torque? It already has good power stock and I could tow with it as is, and I mean one HEAVY trailer! Why? Gears, man, gears! Early vehicles may have had only 50 to 100 hp and pitiful torque but they made trucks for hauling and they worked: gears.

Seems to me, and what made me to decide to build mine as is, was that gears were what I needed no matter what. NV4500 with 4.1 does the job just fine and I can cruise right down the freeway at any reasonable speed. I haven't done an accurate mileage check yet but know I'm getting around 30 or better mpg around town! I don't have to worry about a 6BT eating up all my hard work and bank account on broken parts and fuel.

By the time you got to your 3rd trany and 2nd transfer case and several clutches and probably some broken axles I'll bet you'd wi$h you had installed a 4BT?
 

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I would imagine that by backing out the fuel screw you could back that down a bit but you could run into a lean mixture & increased exhaust gas temperature if you went too far. (Blacksmith bellows effect) I think you could back her down to the 120-130 hp range and end up in the neighborhood of 30 mpg or more.
Sorry man but that's wrong. Only petrol engines work that way.
Diesels always run lean, the exhaust gas temps drop as fuel loading drops. There is no problem at all with giving a diesel less fuel.

Detuning for the drivetrain is fine and the six cylinder is going to be a much smoother and sweeter engine than a four cylinder.
However for fuel economy the 4BT is going to win unless highly stressed. The reason is as simple as fewer moving parts and less internal friction.
 

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Discussion Starter · #7 ·
I'm going think about it a little more.. This will be my 2nd 4BT swap so I have some time with them.. I did some towing with the last one, I did actually tow some cars, etc.. This one will be a stronger truck but bottom line is it is still mostly a 1/2 ton truck, and with the 4BT, it felt like a 1/2 ton...

I have seen a couple of these 80's era FJ60's with the 6BTs in them... Again this one would be minimally lifted, basically look identical to the one posted, probably a NV4500, the stock t case (which is very strong) and land cruiser axles are actually also very strong. Not really off roaded (but capable of light stuff), and 32' tires or so I figure.. Goal being speed, smoothness, etc.. I don't have the 6BT yet either so I can be flexible about this. But seemed like the later 90s era 6BTs would be better.. I think it will be fine, but again will think a little more about this.. This would be the tow and hauling rig for the most part...
 

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Someone not far from me put an Isuzu 6BD1T into a Jag XJ6.

He had to dry-sump it to get road clearance. Maybe it'll give you some inspiration.
 

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im also thinking of doing a 6bt swap into my 87 fj60. im aware of its length and height so will def need to put at least a 4" lift on it. i just dont know if i will need to swap out the axles too?
 

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Discussion Starter · #10 ·
RE axles, depends on what you will use if for.. Bigger tires, hard off roading, yes probably... 33" or less, mostly mild, probably fine. The LC axles are pretty strong. Also a bunch of companies make aftermarket birfields and shafts which are the weakest area..

Also I've been told you can do less than a 4" with a 6BT and a FJ60.. Luke from 4x4labs.com just put one in a 60, probably has good info..
 

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i probably wont be using it for serious offroading, it will be mostly on the road. how much fabrication is needed? engine mounts? also, is the np205 transfer case used with teh 6bt to mate to a nv4500 5pd tranny?
 

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also, whats the easiest way to get a lift, do i have to replace the stock springs? or is there a way where i can retain them? maybe use add-a-leaf?
 

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Discussion Starter · #13 ·
You probably want aftermarket springs of some sort... Maybe add a leafs in the pack on top of the aftermarket springs.. The 6BT is probably 300-400 lbs more than a stock 2F or 3FE...

Fabrication wise, pretty standard stuff, the motor mounts and the transmission cross member.. Hope it helps.. A


http://forum.ih8mud.com/showthread.php?t=149210
 

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i cant add shackles and maybe an add-a-leaf on my current springs? all the springs were replaced with new factory ones in 99-00 by the previous owner. i dont know why he didnt go with aftermarket for a lift.
 

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i know my 93 reg cab dodge getrag five speed 4x4 driving 180 miles to central ore . empty as far as towing goes and speed at 70mph most of the way gets 21mpg or so. i love it for a full size pu. i have a 84 chev 6.2 diesel 1/2 ton short box 4x4 that i bought new and the rear end went at about 125k i have over 200k on it now and just replaced the 6.2 with a 6.5 crate motor. more power hands down but mileage dropped from 21 down to 19 on a good day hopefully when it gets 30k or so on it it will gain some mileage.
 

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Question on this.. If someone were to put a 6BT in a rig that is ~ half ton, it fits and works well doing it and is clean but some of the axle components might show early fatigue if left at a stock power range.. Also in the effort of FUEL MILEAGE, is this possible with this era 6BT motor, to detune it? Can you detune significantly for better mileage and actually having less overall power?
Install a 'valet switch' to control the AFC to the p-pump. This switch prevents the pump from getting the extra fuel as the turbo builds boost.
 

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G'head, do it

We're going to find out together; I just got my "F-150D" inspected and reliably on the road--1/2T pickups are not supposed to like the 6BT...but the fella that was my inspiration has had total reliability from his 1986 full-size daily-driver Bronco for over 10 years.

That's with an OEM Ford 9" rear end, and an early intercooled 160hp Dodge. Umm, his daughter drives it to high school now...

I've dropped in a '98 2V, 215hp version, stock 8.8 axle with 3.08. The AA RAnger OD/NP435/NP205 was already in the truck, connected via a 4BT/Ford setup--everything bolted right up.

Dodge used a 160hp version of this engine in '94-'95 in their automatic-equipped pickups. I suspect the derating was due to a fuel plate and injector change. Sorta like the big fuel plate/big injectors the big hp guys toss into the P7100, only in the opposite direction.

Eddie
 
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